Surfactants in detergent products typically create a significant volume of suds during wash. During subsequent rinsing steps, the suds and excessive surfactants are rinsed off together with soil and other debris.
Sudsing profile of a detergent composition is important for the consumer experience, where the appropriate volume and speed of suds formation, retention and disappearance in the wash and rinse cycles are considered key benchmarks of cleaning performance by the consumers.
A large volume of suds is initially desirable, especially during a hand washing process where the user is directly involved with the wash, feeling and touching the suds generated by the detergent composition. Copious suds during the wash is viewed by the consumers as the primary and most desirable signal of cleaning, as it indicates to the user that sufficient surfactant is present, working to clean the articles (e.g., fabric or dishes).
Paradoxically, while a large volume of suds is desirable during the wash cycle of a cleaning process, it is nevertheless undesirable during the rinse cycle. If a high volume of suds is still present during the rinse cycle, the consumers immediately infer from it that there may still be surfactant residue left on the articles and that the articles are not yet “clean”. As a result, the consumers will feel the need to rinse multiple times until the suds completely disappear. Sometimes, it can take between 3-6 rinses in order to remove such suds to the satisfaction of the consumer. This adds up to a greater consumption of water. Typically, about 5-10 tons of water is consumed per year per household in countries such as India and China, where habits of hand-washing fabric or dishes are more prevalent than machine-washing. Because water is often a limited resource, especially in those hand-washing countries, the excess amount of water consumed by multiple rinses reduces the amount of water available for other possible uses, such as irrigation, drinking, bathing, etc.
However, it has been found that fewer rinses can sufficiently remove surfactants, and thus multiple rinses are not necessary. Therefore, if the above-described consumer perception can be successfully overcome, the number of rinsing can be reduced with little or no adverse effects to the end cleaning result.
Various foam-control or anti-foaming agents have been added to detergent or cleaning compositions to control and reduce suds volume. For example, U.S. Pat. No. 8,536,109 (Dow Corning) discloses a foam control composition that contains a silicone anti-foam dispersed in an organopolysiloxane resin, wherein the silicone anti-foam includes an organopolysiloxane, an organosilicon resin, and a hydrophobic filler; U.S. Pat. No. 7,566,750 (Wacker) discloses a defoamer composition containing an organopolysiloxane, filler particles and/or an organopolysiloxane resin, and a very minor amount of added water, which is more effective in reducing the foam or suds volume.
There is a continuing need for improved foam control or anti-foaming agents that can further reduce suds, especially those that can more effectively suppress or kill suds during the rinse cycle of a cleaning process, to thereby minimize the amount of water needed for rinse, and preferably to enable “single rinse” of the to-be-cleaned article. Cleaning compositions containing such improved foam control or anti-foaming agents are particularly desirable for cost saving and environmental conservation purposes.